[STANDARDS] Ramachandran Ramjee Microsoft Research India Sumit Roy University of Washington USA Krishna Chintalapudi Microsoft Research USA Editor: Michelle Gong A CRITIQUE OF FCC’S TV WHITE SPACE REGULATIONS roadband access constitutes the “oxygen” for the Internet Era, to which end, the issue of spectrum management is foundational. In this position paper, we present an overview Bof FCC’s pioneering work framing TV white space rules that allows unlicensed access by secondary users while protecting licensed primary users. The core contribution of this paper is an in-depth analysis of FCC’s TV white space regulations (often treated as a global template). We argue that FCC’s current white space regulations does not achieve the desired balance between effectively promoting unlicensed secondary access and providing adequate protection of the primary. As more countries around the world look at framing white space regulations, we argue for incorporating a more flexible design that can catalyze a white space device ecosystem to flourish, similar to Wi-Fi. INTRODUCTION network services, based on the operators Broadly speaking, spectrum allocations belief that exclusive rights to spectrum can be classified under two principles/ enables them to offer/tailor desired approaches: services, as well as optimize the network/ delivery mechanisms so as to extract a) granting of exclusive licenses, usually via maximum revenue. The unlicensed model a suitably designed auction mechanism, is used by standards, such as Wi-Fi, to operators for an explicitly identified where the fundamental issue is managing purpose of service (that may not be interference, specifically a) secondary changed) and unlicensed interference to primary b) setting aside “unlicensed bands” for licensed users and b) interference between technology neutral usage, whereby unlicensed secondary users. FCC Part 15 compliant devices do not need a license rules [FCC 01-58] that govern unlicensed to operate (but must nevertheless be bands have mostly focused on “transmit certified), akin to a public “commons.” power” centric rules to ensure limited interference from secondary unlicensed The first scenario conforms to a single users to primary users (e.g. limits on primary network in the licensed band average transmit power over the band, whereas the latter maps to multiple (co- maximum power spectral density and on located) networks. The exclusive license out-of-band emission limit using transmit model is the operative one for all cellular spectral mask) while encouraging the use bigstockphoto.com Photo, 20 GetMobile January 2016 | Volume 20, Issue 1 [STANDARDS] of “etiquettes,” such as listen before talk TV WHITE SPACES & RULES above 512 MHz (above TV channel 20) (LBT) for managing interference between OF “COGNITIVE USAGE” if those available channels are adjacent to unlicensed secondary users.1 After the transition from analog to digital occupied TV channels. Fixed TVBDs can Spectrum license auctions, such as TV broadcasting, TV broadcast in the U.S. utilize an external antenna up to 30 meters those by the FCC, typically generate several is limited to channels 2-51; the unused above the ground and are allowed a higher billion USD as a one-time revenue to spectrum within channels 2-51 at any transmitter power of 1W or up to 4W EIRP the U.S. treasury (e.g. 2006 auction of 90 location is designated as TV White Spaces with a 6 dBi gain antenna. These devices MHz netted USD 14 billion [BULOW]). (TVWS). The FCC, in a series of pioneering are not allowed to be located at a site where However, a multibillion dollar industry notices and regulations starting from 2004, the ground height above the average terrain has also grown in the use of “unlicensed” effectively allowed Part 15 like (unlicensed) (HAAT) exceeds 250 meters, so use in hilly spectrum [THANKI 1]; a recent analysis operation in TV White Space frequencies areas may be restricted. suggests that the value generated from subject to cognitive usage rules for protect- unlicensed spectrum use is $140 billion ing the primary users, i.e. requiring un- Personal/Portable Devices: Personal/ per annum in the U.S. alone [THANKI licensed or secondary TV Band (TVBD) portable device transmissions are restricted 2]. Because users of unlicensed spectrum devices to incorporate ‘‘smart radio’’ features to available channels in the frequency bands enjoy economies of scale and do not pay to protect the primary users [FCC 04-113, 512‐608 MHz (TV channels 21‐36) and for expensive spectrum licenses, unlicensed FCC 08-260, FCC 10-174, FCC 14-144]. 614‐698 MHz (TV channels 38‐51). These networks typically offer a less expensive and devices are limited to a maximum EIRP of more readily deployable form of wireless General Requirements on TV Band 100mW or 40mW if the device is operating service than licensed spectrum – albeit Devices (TVBDs) [FCC 14-144] on a channel adjacent to an occupied TV at a trade-off for quality of service and The unlicensed TVBDs were classified channel. protection from interference. into two functional categories: a) lower Wi-Fi carried about 70% of all mobile power ‘‘personal/portable’’ devices, such as Mode I Personal/Portable Devices: Internet data traffic in 2014 and Wi-Fi’s Wi-Fi–like cards in laptop computers and A Mode I device is not required to use share is expected to rise to 85% by 2018 b) higher power ‘‘fixed’’ devices that could geo‐location or have access to the TV [WI-FI-TRENDS]. The global success of be used to provide services such as 802.22 bands database. Instead, it obtains a list of Wi-Fi even with the relatively small ranges Base station/CPEs providing a backhaul for available channels from either a fixed or of frequency allocated for unlicensed use broadband client access. Mode II personal/portable device. A Mode has led many spectrum advocates to press The personal/portable TVBDs were I device may not initiate a network nor for more unlicensed spectrum, leading to a further sub-divided into Mode I and Mode may it provide a list of available channels more equitably mixed ecosystem of licensed II operations with somewhat different rules to another device. and unlicensed approaches that combines applying as detailed below. Fixed devices are the relative strengths of both. While the intended to operate at a fixed location (e.g. Mode II Personal/Portable Devices: A original notion of (pure) unlicensed usage an outdoor access point) while personal/ Mode II device uses its own geo‐location corresponds to a “commons” scenario portable devices can operate in unspecified capability and access to the TV bands where all networks are treated on-par and locations based on user mobility. A (second- database, either through a direct connection must accept interference from each other, ary) network can only be initiated by a fixed to the Internet or through an indirect rule making can readily accommodate or Mode II TVBD, not a Mode I TVBD. connection by way of a fixed TVBD or provisioning of priority for any sub-set another Mode II TVBD. A Mode II device operating in co- or adjacent channels.2 Fixed Devices: Fixed devices can initiate may select a channel itself and initiate and This is precisely the notion of Cognitive a network by sending enabling signals operate as part of a network of TVBDs, White Spaces (WS), whereby the identified to one or more fixed and/or personal/ transmitting to and receiving from one or primary services are to be protected from portable TVBDs. Fixed devices can use any more fixed or personal/portable TVDBs. unlicensed usage, as we discuss next. available WS frequency but may not operate It may provide a list of available channels to a Mode I device. 1 This is in contrast to EU regulations that mandate LBT use in unlicensed spectrum. 2 For example, in the upper 5 GHz band, Wi-Fi devices share the band with military radar subject to Interference Avoidance Methods: Channel the condition that the Wi-Fi devices are capable of spectrum sensing and if radar is detected, the availability for a TVBD is determined based unlicensed user must immediately vacate the channel. upon geo‐location and database access but January 2016 | Volume 20, Issue 1 GetMobile 21 [STANDARDS] spectrum sensing can also be used. For fixed a handful of small startups [TVBD]. The and Mode II devices, geographic coordinates integration of embedded WS devices into need to be determined to an accuracy of consumer portable/handheld devices has +/‐ 50 meters by utilizing incorporated not yet occurred, stalling the onset of any geo‐location capability. Fixed devices that virtuous market cycle based on increasing are professionally installed do not need adoption volume. As a result, the future geo‐location capability if the coordinates of WS technology under the regulations are provided at time of installation. All proposed by FCC looks bleak. devices must register their coordinates with In this section, building upon some the database and must re‐establish their preliminary observations in [TCCN 2015], position each time it is activated from a we provide an in-depth assessment for this power‐off condition. Fixed devices shall state-of-affairs and suggest alternate designs access and update their database at least that could allow a large white space device once every day and personal/portable device FIGURE 1. One of the first FCC-approved white ecosystem to develop, similar to that of must check its location at least once every spaces device is a 1.5-lb radio from KTS Wireless. Wi-Fi. 60 seconds. Operation on a channel must cease immediately if the database indicates ISSUES WITH FCC TVWS RULINGS the channel is no longer available. Mode 1. Database showing little or no white II personal/portable devices also must incumbents [SHELL 11].